Bonded optical devices

ABSTRACT

A bonded optical device is disclosed. The bonded optical device can include a first optical element, a second optical element, and an optical pathway. The first optical element has a first array of optical emitters configured to emit light of a first color. The first optical element is bonded to at least one processor element, the at least one processor element including active circuitry configured to control operation of the first optical element. The second optical element has a second array of optical emitters configured to emit light of a second color different from the first color. The second optical element is bonded to the at least one processor element. The optical pathway is optically coupled with the first and second optical elements. The optical pathway is configured to transmit a superposition of light from the first and second optical emitters to an optical output to be viewed by users.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/949,312, filed Dec. 17, 2019, the entire contents of which arehereby incorporated by reference in their entirety and for all purposes.

BACKGROUND Field of the Invention

The field relates to bonded optical devices and, in particular, tobonded optical devices for use in wearable electronics.

Description of the Related Art

In some types of display devices, a very small and extremely highresolution device is desirable. Examples include directly viewed displayscreens, such as smart watches and cell phone displays, as well asapplications with projected images from small screens, such as heads-updisplays (HUDs) and smart glasses. For example, in wearable smartglasses, such as augmented reality (AR) glasses, or other eyewear thatincludes electronic circuitry and a display, the image may be positionedless than 1-2 cm (e.g., 1-1.2 cm) from the user's eye. In such devices,it can be desirable to utilize a pitch for the display pixels that areas small as possible (e.g., less than 5-6 μm), for example, in order toprovide a desired quality of image. Some technologies, such as liquidcrystal-on-silicon (LCoS) may be able to provide pixels with lowpitches, but are inefficient in that an insignificant amount of opticalenergy (e.g., light) is lost, may have low manufacturing yield, lowerresolution and may be expensive.

Other technologies such as micro light emitting diodes (microLED) arecapable of providing very bright images for AR/MR (Mixed Reality)applications because they can provide a sufficient amount of opticalenergy (e.g., brightness) to provide, e.g., a clear image visible inwell-lit ambiance. Light Emitting Diode (LED) wafers can be processedfor one wavelength of light at a time (red “R”, green “G” or blue “B”),and making a multi-colored display still poses a challenge againstproviding a desired level of image quality in the aforementionedapplications.

Accordingly, there remains a continuing need for improved opticaldevices, for example to create a colored image from monochromatic LEDdisplays and integrate these monochromatic microLED displays forapplications such as AR smart glasses, projection systems, car HUDs,smart watch displays, cell phone displays, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific implementations will now be described with reference to thefollowing drawings, which are provided by way of example, and notlimitation.

FIG. 1 is a diagram showing an illustration of relative distancesbetween a display device and a user's eye.

FIG. 2 is a schematic side sectional view of directly bonded opticaldevices, according to an embodiment.

FIG. 3 is a schematic side sectional view of directly bonded opticaldevices, according to another embodiment.

FIG. 4 is a schematic side sectional view of an optical assembly,according to an embodiment.

FIG. 5 is a schematic side sectional view of an optical assembly,according to another embodiment.

FIG. 6 is a diagram showing an illustration of physical separationbetween pixels within an optical device, according to an embodiment.

FIG. 7A is a diagram showing an illustration of physical separationbetween individual pixels of an optical device, according to anembodiment.

FIG. 7B is a diagram showing an illustration of physical separation onlyin an A×A matrix of pixels within an optical device, according to anembodiment.

FIG. 8 is a diagram showing an optical system that can incorporate theoptical assemblies described herein, according to an embodiment.

FIG. 9 is a diagram showing optical devices directly bonded to awaveguide with input and output couplings, according to an embodiment.

FIG. 10 is a diagram showing optical devices configured to direct lightto a waveguide with input and output couplings, according to anotherembodiment.

FIG. 11 is a diagram showing an illustration of superposition of threecolor pixels.

DETAILED DESCRIPTION

FIG. 1 is a diagram showing an illustration 100 of the relative displaydistances between various display devices 104, 106, 108 and a user's eye102. The most sensitive part of the eye, fovea, contains the most cones(which help us identify colors), and has a resolution of ˜1 arc-minute,which is 60 pixels-per-degree (PPD). PPD identifies the pixel pitchneeded in a display based on a distance of the display device from theuser's eye 102. For an AR smart glass display 104 with working distanceof ˜1 cm from the user's eye 102, a pixel pitch of ˜5 μm produces whatis perceived as a “clear image.” For a cell phone display 106 with aworking distance of ˜20 cm from the user's eye 102, a pixel pitch of ˜50μm produces a clear image. For a computer display 108 with a workingdistance of ˜50 cm from the user's eye 102, a pixel pitch of ˜300 μmproduces a clear image. Digital Light Processing (DLP) and liquidcrystal-on-silicon (LCoS) based technologies are not sufficient forseveral reasons, including, e.g., low brightness, pixel size, pitch,display size, etc. Accordingly, microLED devices may be beneficial insome applications, such as AR display applications.

Various embodiments disclosed herein relate to bonded optical devices200, 300 a-c (shown in, e.g., FIGS. 2 and 3 ). As explained herein, sometypes of optical elements 202 a-c, 302 a-c (shown in, e.g., FIGS. 2 and3 ), particularly light emitting elements (e.g., light emitting diodes,or LEDs), may be fabricated in wafers having devices configured to emitlight of a single color (e.g., red, green, or blue), which can makefabrication of multi-colored displays comprised of several hundredthousand or millions of LEDs from these separate wafers, challenging. Invarious embodiments, the optical elements 202 a-c, 302 a-c can be formedof a semiconductor material. For example, optical wafers (such as LEDwafers) can be formed from a Group III-V compound semiconductormaterial(s), such as InP, GaN, AlGaAs, InGaN, AlGaInP, etc. In variousembodiments, direct bonding procedures can enable such compoundsemiconductor materials to be bonded to a different type ofsemiconductor processor element (e.g., a Si or CMOS processor die),creating a heterogenous system. Furthermore, it can be challenging toprovide optical elements 202 a-c, 302 a-c (shown in, e.g., FIGS. 2 and 3) that have pixels 602 a-c (shown in, e.g., FIG. 6 ) (or displayregions) having a sufficiently small pitch (e.g., space between pixels)for displaying high quality and high brightness images to be directlyviewed or projected on displays (such as small displays or displaysconfigured to be positioned close to the user). In various embodiments,a pitch of the optical emitters of an array can be less than 50 microns,e.g., less than 10 microns.

In some microLED displays, each pixel 704 (shown in, e.g., FIG. 7A) canutilize individual LED chips (e.g., optical elements) as a pixel 704(shown in, e.g., FIG. 7A) or sub-pixel. For example, microLED chips(e.g., optical elements including array(s) of emitters) can beseparately manufactured and positioned with pick-and-place techniques.Transfer and placement techniques and color conversion schemes can alsobe used but these techniques may not be economical or may be very lossy.Accordingly, there remains a continuing need for improved opticaldevices.

Embodiments disclosed herein can enable displays having a fine pixelpitch by bonding (e.g., directly bonding or hybrid bonding) an opticalelement 202 a-c, 302 a-c (shown in, e.g., FIGS. 2 and 3 ) (particularlya light emitting element such as an LED device including a plurality ofLEDs) to at least one carrier 204, 304 a-c (shown in, e.g., FIGS. 2 and3 ), such as a processor, e.g., an image processor element that caninclude active circuitry (e.g., one or more transistors) configured tocontrol the operation of the optical element 202 a-c, 302 a-c (shown in,e.g., FIGS. 2 and 3 ). In various embodiments, the optical emitters ofthe emitter arrays can be independently controllable. Beneficially, insome embodiments, direct bonding or hybrid bonding can be used tophysically and electrically connect the optical element 202 a-c, 302 a-c(shown in, e.g., FIGS. 2 and 3 ) to the carrier 204, 304 a-c (shown in,e.g., FIGS. 2 and 3 ) (e.g., processor element) without an adhesive. Theuse of direct bonding can enable pixel pitches of less than 5 microns,or less than 1 micron. The at least one carrier 204, 304 a-c has acoefficient of thermal expansion (CTE) less than 7 ppm.

FIG. 2 is a schematic side sectional view of a bonded optical device 200in which a plurality of optical elements 202 a-c are bonded (e.g.,directly bonded) to a common carrier 204 according to one embodiment. Insome embodiments, the common carrier 204 can comprise an integrateddevice die, such as a processor die having circuitry that controlsoperation of the optical elements 202 a-202 c. FIG. 3 is a schematicside sectional view of a plurality of bonded optical devices 300 a-c inwhich a plurality of optical elements 302 a-c are bonded (e.g., directlybonded) to a corresponding plurality of carriers 304 a-c. The opticalelements can be manufactured in wafer form and singulated to define theoptical elements 202 a-c, 302 a-c shown in FIGS. 2-3 . As shown in FIG.2 , the optical elements 202 a-c (which can comprise emitter dies, suchas LEDs) can be directly bonded to a common carrier 204 without anintervening adhesive, in for example a die-to-wafer (D2W) process. Insome embodiments (see, e.g., FIG. 11 ), the optical elements 202 a-c,302 a-c and carrier 204, 304 a-c can be integrated into a larger opticalsystem. For example, the bonded optical device 200 (including, e.g., theoptical elements 202 a-c and the common carrier 204 directly bondedthereto) can be mounted to a waveguide or other structure.

In other embodiments, the carrier 304 a-c can be singulated to form aplurality of bonded optical devices 300 a-c, as shown in FIG. 3 . Inother embodiments, the singulated optical elements 302 a-c can be bondedto the singulated carriers 304 a-c in a die-to-die (D2D) process toobtain the bonded optical devices 300 a-c shown in FIG. 3 . In stillother embodiments, the optical elements in wafer form (not shown) can bebonded (e.g., directly bonded) to the carrier in wafer form (not shown)(e.g., processor wafer) in a wafer-to-wafer (W2W) process (not shown).The bonded wafers can then be singulated to form a plurality of bondedoptical devices 300 a-c.

The optical element(s) 202 a-c, 302 a-c can be directly bonded (e.g.,using dielectric-to-dielectric bonding techniques, such as the ZiBond®,DBI or DBI Ultra techniques used by Xperi Corporation of San Jose,Calif.) to the at least one carrier 204, 304 a-c (such as a processorelement) without an adhesive. For example, the dielectric-to-dielectricbonds may be formed without an adhesive using the direct bondingtechniques disclosed at least in U.S. Pat. Nos. 9,391,143 and10,434,749, the entire contents of each of which are incorporated byreference herein in their entirety and for all purposes.

In various embodiments, the direct bonds can be formed without anintervening adhesive. For example, dielectric bonding surfaces 206, 306a-c can be polished to a high degree of smoothness. The bonding surfaces206, 306 a-c can be cleaned and exposed to a plasma and/or etchants toactivate the surfaces. In some embodiments, the surfaces can beterminated with a species after activation or during activation (e.g.,during the plasma and/or etch processes). In various embodiments, theterminating species can comprise nitrogen. Further, in some embodiments,the bonding surfaces can be exposed to fluorine. For example, there maybe one or multiple fluorine peaks near layer and/or bonding interfaces.Without being limited by theory, in some embodiments, the activationprocess can be performed to break chemical bonds at the bonding surface,and the termination process can provide additional chemical species atthe bonding surface that improves the bonding energy during directbonding. Thus, in the directly bonded structures, the bonding interfacebetween two dielectric materials can comprise a very smooth interfacewith higher nitrogen content and/or fluorine peaks at the bondinginterface.

In various embodiments, conductive contact pads 208 a-c, 308 a-c of theoptical element 202 a-c, 302 a-c or LED element can be directly bondedto corresponding conductive contact pads 210 a-c, 310 a-c of the carrier204, 304 a-c (e.g., a processor element). One LED pixel within an LEDchip may have two contact pads or electrodes (positive electrode andnegative electrode) in various embodiments. In various embodiments, thecarrier 204, 304 a-c (e.g., processor element) can create identicalimages on the optical corresponding elements 302 a-c. As explainedherein, each optical element 302 a-302 c can comprise a monochromaticlight emitting element, and can create identical images, such that, whenthe images are superimposed, a multi-colored image can be viewed. Forexample, a hybrid bonding technique can be used to provideconductor-to-conductor direct bonds along a bond interface 206, 306 a-cthat includes covalently direct bonded dielectric-to-dielectricsurfaces. In various embodiments, the conductor-to-conductor (e.g.,contact pad to contact pad) direct bonds and thedielectric-to-dielectric bonds can be formed using the direct bondingtechniques disclosed at least in U.S. Pat. Nos. 9,716,033 and 9,852,988,the entire contents of each of which are incorporated by referenceherein in their entirety and for all purposes.

For example, dielectric bonding surfaces 206, 306 a-c can be preparedand directly bonded to one another without an intervening adhesive.Conductive contact pads 208 a-c, 210 a-c, 308 a-c, 310 a-c (which may besurrounded by nonconductive dielectric field regions) may also directlybond to one another without an intervening adhesive. In someembodiments, the respective contact pads 208 a-c, 210 a-c, 308 a-c, 310a-c can be recessed below the dielectric field regions, for example,recessed by less than 20 nm, less than 15 nm, or less than 10 nm, forexample, recessed in a range of 2 nm to 20 nm, or in a range of 4 nm to10 nm. The dielectric field regions can be directly bonded to oneanother without an adhesive at room temperature in some embodiments and,subsequently, the bonded structure can be annealed. Upon annealing, thecontact pads 208 a-c, 210 a-c, 308 a-c, 310 a-c can expand and contactone another to form a metal-to-metal direct bond. Beneficially, the useof Direct Bond Interconnect, or DBI®, and/or ZiBond techniques canenable fine pixel pitches as explained above. In some embodiments, thepitch of the bonding pads 208 a-c, 210 a-c, 308 a-c, 310 a-c may be lessthan 300 microns, less than 40 microns or less than 10 microns, or evenless than 2 microns. For some applications the ratio of the pitch of thebonding pads 208 a-c, 210 a-c, 308 a-c, 310 a-c to one of the dimensionsof the bonding pad 208 a-c, 210 a-c, 308 a-c, 310 a-c is less than 5, orless than 3 and sometimes desirably less than 2. In various embodiments,the contact pads 208 a-c, 210 a-c, 308 a-c, 310 a-c can comprise copper,although other metals may be suitable.

The embodiments disclosed herein can also be used in combination withthe devices and methods disclosed throughout U.S. patent applicationSer. No. 15/919,570 (which issued as U.S. Pat. No. 10,629,577 on Apr.21, 2020); Ser. No. 16/219,693; and Ser. No. 16/176,191, the entirecontents of each of which are incorporated by reference herein in theirentirety and for all purposes. U.S. patent application Ser. No.15/919,570, for example, teaches methods for direct hybrid bonding ofCMOS logic wafers or dies to LED wafers or dies for direct control ofthe emitters (active matrix driving). U.S. application Ser. No.16/176,191 teaches direct bonding of optically transparent substrates.

The embodiments disclosed herein can further be used in combination withthe devices and methods (which describe how an optical element can bebonded to a processor die) disclosed throughout U.S. Pat. No.10,629,577, the entire contents of which are incorporated by referenceherein in their entirety and for all purposes. U.S. Pat. No. 10,629,577teaches direct-bonded arrays of optical elements such as for exampledirect-bonded LED arrays.

Thus, in direct bonding processes, a first element (e.g., an opticalelement 202 a-c, 302 a-c) can be directly bonded to a second element(e.g., a carrier 204, 304 a-c such as a processor die) without anintervening adhesive. In some arrangements, the first element cancomprise a singulated element, such as a singulated optical device die.In other arrangements, the first element can comprise a carrier orsubstrate (e.g., a wafer) that includes a plurality (e.g., tens,hundreds, or more) of device regions that, when singulated, form aplurality of integrated device dies. Similarly, the second element cancomprise a singulated element, such as a singulated integrated devicedie (e.g., a processor die). In other arrangements, the second elementcan comprise a substrate (e.g., a wafer).

As explained herein, the first and second elements (e.g., the opticalelement 202 a-c, 302 a-c and the carrier 204, 304 a-c or processor die)can be directly bonded to one another without an adhesive, which isdifferent from a deposition process. The first and second elements canaccordingly comprise non-deposited elements. Further, directly bondedstructures, unlike deposited layers, can include a defect region (notshown) along the bond interface 206, 306 a-c in which nanovoids arepresent. The nanovoids may be formed due to activation of the bondingsurfaces (e.g., exposure to a plasma). As explained above, the bondinterface 206, 306 a-c can include concentration of materials from theactivation and/or last chemical treatment processes. For example, inembodiments that utilize a nitrogen plasma for activation, a nitrogenpeak can be formed at the bond interface 206, 306 a-c. In embodimentsthat utilize an oxygen plasma for activation, an oxygen peak can beformed at the bond interface 206, 306 a-c. In some embodiments, the bondinterface 206, 306 a-c can comprise silicon oxide, silicon nitride,silicon oxynitride, silicon oxycarbonitride, or silicon carbonitride. Asexplained herein, the direct bond can comprise a covalent bond, which isstronger than van Der Waals bonds. The bonding layers can also comprisepolished surfaces that are planarized to a high degree of smoothness.

In various embodiments, the metal-to-metal bonds between the contactpads 208 a-c, 210 a-c or 308 a-c, 310 a-c can be joined such that coppergrains grow into each other across the bond interface 206, 306 a-c. Insome embodiments, the copper can have grains oriented along the crystalplane for improved copper diffusion across the bond interface 206, 306a-c. The bond interface 206, 306 a-c can extend substantially entirelyto at least a portion of the bonded contact pads 208 a-c, 210 a-c, 308a-c, 310 a-c, such that there is substantially no gap between thenonconductive bonding regions at or near the bonded contact pads 208a-c, 210 a-c, 308 a-c, 310 a-c. In some embodiments, a barrier layer(not shown) may be provided under the contact pads 208 a-c, 210 a-c, 308a-c, 310 a-c (e.g., which may include copper). In other embodiments,however, there may be no barrier layer under the contact pads 208 a-c,210 a-c, 308 a-c, 310 a-c, for example, as described in U.S. PatentApplication Publication No. US 2019/0096741, which is incorporated byreference herein in its entirety and for all purposes.

Although the illustrated embodiments show directly bonded opticalelements, in other embodiments, the optical devices can be attached tothe carrier(s) with an adhesive, e.g., a transparent adhesive.

As illustrated and described herein, in some embodiments, the bondedoptical device 200, 300 a-c can comprise an optical element 202 a-c, 302a-c that includes a plurality of image regions or display regions (e.g.,pixels 602 a-c as shown in FIG. 6 ). Each image region can comprise amonochromatic image region that includes an optical emitter 614configured to emit light of a single color. The optical emitter 614 cancomprise a light emitting diode, which can emit light from the region orsurface in the optical element in which the LED is formed. The opticalelement 202 a-c, 302 a-c may comprise a LED wafer comprising Group III-Vmaterials, e.g. GaAs, GaN, GaP, InGaN, AlGaInP, AlGaAs, etc. Forexample, the optical element 202 a-c, 302 a-c can comprise monochromaticLED chips in various embodiments. The LED chips can each be configuredto emit light of a single color. The LED chips can be configured to emitdifferent colors from one another. For example, a first LED chip (suchas the optical element 202 a) can be configured to emit red light, asecond LED chip (such as the optical element 202 b) can be configured toemit green light, and a third LED chip (such as the optical element 202c) can be configured to emit blue light. It should be appreciated thatthe LED chips can emit any suitable colors.

The optical element 202 a-c, 302 a-c can be bonded, e.g., directlybonded without an intervening adhesive, to at least one carrier 204, 304a-c (for example, at least one processor element) that has activecircuitry for controlling operation of pixels of the optical element 202a-c, 302 a-c. The at least one carrier 204, 304 a-c can comprise asemiconductor element, such as silicon, in various arrangements. Forexample, the carrier 204, 304 a-c can serve as a silicon-based backplanein some embodiments. The carrier 204, 304 a-c can comprise a processordie having driver circuitry electrically connected to the opticalemitters by way of the contact pads 208 a-c, 210 a-c, 308 a-c, 310 a-c.The driver circuitry can control the emission of light from theplurality of optical emitters of the optical element 202 a-c, 302 a-c.

As explained herein, the plurality of image regions (such as the pixels602 a-c shown in FIG. 6 ) can be arranged relative to one another and toa common optical pathway (such as an optical waveguide 804 shown in FIG.8 ) such that monochromatic light from each image region is coupled intothe optical pathway. In some embodiments, a plurality of such bondedoptical devices 200, 300 a-c can be coupled with the common opticalpathway. The plurality of bonded optical devices 200, 300 a-c can beconfigured to emit light of different colors (e.g., a red bonded opticaldevice, a green bonded optical device, a blue bonded optical device). Asuperimposed light beam from the plurality of bonded optical devices canbe transferred along the optical pathway to an optical output to beviewed by a user. A plurality of monochromatic images can besuperimposed into a polychromatic image in the waveguide representativeof the combined contribution of the pixels each of the plurality ofbonded optical devices.

In various embodiments, the superposition of light from multiplemonochromatic image regions can provide redundancy in case one imageregion is damaged or unused. In such cases, light from the other pixelscan compensate for the color of light in the damaged image region.

Beneficially, the embodiments disclosed herein can utilize bondedoptical elements 202 a-c, 302 a-c that include an array or pixels ofmultiple LEDs, without separately singulating and repopulating thesingulated LEDs on a substrate. The array of LED chips can be directlybonded to an array of processing elements configured to controloperation of the LEDs. By contrast, in other methods, each LED pixel canbe singulated and stacked on a substrate at higher pitches, which cancomplicate assembly processes. The use of directly bonded opticalelements including an array of LEDs can accordingly improvemanufacturability of display devices. In one example the array of red(R), Green (G) and Blue (B) LED wafers are each separately direct orhybrid bonded to silicon (Si) backplane or imager wafers. These stackscan then be singulated to form red, green and blue monochromaticimagers, which could be combined to form a multi-colored image. Inanother example, red, green, and blue LED wafers can be separatelysingulated to form R, G, B LED chips and can be direct bonded to onesilicon backplane or imager. Elements in a silicon backplane can beelectrically connected to LED pixels within R, G, B chips to achievepixel level control. Although LED wafers can be direct or hybrid bondedto a silicon backplane, any other suitable backplane (e.g., a Thin FilmTransistor, or TFT) backplane may also be used. In some embodiments, asexplained herein, an optical assembly can comprise at least one red LEDchip, at least one green LED chip, and at least one blue LED chip. Insome embodiments, an optical system can comprise a plurality or an arrayof multiple such optical assemblies to direct image data to the user.

In some embodiments, the monochromatic image regions can be orientedparallel to one another. For example, in some embodiments, the imageregions can be positioned laterally side-by-side on a waveguide. Lightfrom the image regions can be coupled into the waveguide, and thewaveguide can transmit a superimposed image of multiple colors to theuser. In other embodiments, the image regions can be positionednon-parallel to one another (e.g., perpendicular to one another), andcombiner optics can be provided to transmit a superimposed image ofmultiple colors to the user.

FIG. 4 is a schematic side sectional view of an optical assembly ofcombined optical devices (e.g., monochromatic emitter chips), accordingto one embodiment. The optical assembly 400 includes a plurality ofoptical devices 400 a-c formed by a plurality of optical elements 402a-c (such as, e.g., monochromatic LED chips) directly bonded to acorresponding plurality of carrier elements 404 a-c (such as, e.g.,silicon-based backplane). The optical assembly 400 can include as aredirection element or mirroring apparatus 406 a-b (e.g., a mirror,beamsplitter or other suitable optical redirection device) and anoptical combiner apparatus 408 (e.g., a lens).

In one embodiment, the optical devices 400 a-c (including the opticalelements 402 a-c (e.g., monochromatic LED chips, for example, for R, G,B, respectively) with corresponding carrier elements 404 a-c (e.g.,silicon backplane) can be combined to form a colored image or portion ofa colored image. That is, instead of for example RGB microLED displays,separate monochromatic LED chips can be combined as shown in FIG. 4 .With three (3) displays used, issues such as gang bonding of millions ofpixels are not a concern. Multiple optical assemblies 400 may beincorporated in an array in various optical systems.

In one implementation, the bonded optical devices 400 a-c can beoriented at an angle relative to one another. For example, the opticalelements 402 a-c can be approximately perpendicular to one another. Inanother implementation, the optical elements 402 a-c can form aprescribed angle that is greater or less than 90° relative to oneanother. The optical devices 400 a-c can each be mounted on a frame orother structure (not shown) and aligned relative to one or moremirroring apparatus 406 a-b (which can be for example beam splitters forredirecting light). As shown in FIG. 4 , the mirroring apparatus 406 a-bcan redirect the light from the optical elements 402 a-c along a commonchannel so as to superimpose the colored light from each optical element402 a-c. The light from each optical element 402 a-c can be varied,based on for example control via the circuitry of the carrier elements404 a-c, so as to generate a superimposed light of various colors. Theimage data of the light from each optical element 402 a-c can passthrough an optical combiner apparatus 408 (e.g., a lens) to collect thelight and transfer it to the user.

In one implementation, hybrid direct bonding (such as DBI®) can beimplemented to bond the carrier elements 404 a-c (e.g., CMOS circuit) tocontrol each pixel/diode at ˜5 μm pitch with the optical elements 402a-c such as large R, G and B chips based on the size of the display.

In another implementation, the colors as produced by the opticalelements 402 a-c as driven by the carrier elements 404 a-c can be usedto deliver an image or portion of an image to the user's eye by theoptical combiner apparatus 408 (such as via curved combiners orwaveguides).

In other implementations, D2D, W2W or D2W bonding can be used, based onthe application.

FIG. 5 is a schematic side sectional view of an optical assemblyincluding combined optical devices, according to another embodiment. Theoptical assembly 500 includes individual optical elements 502 a-c (e.g.,optical wafers, etc.) and carrier elements 504 a-c, as well as mirroringapparatus 506 a-c and optical combiner apparatus 508.

As shown, the individual optical elements (such as for example R, G, Bwafers) 502 a-c can be stacked on carrier elements 504 a-c andsingulated to form three (3) large optical devices such as monochromaticdisplay chips with for example size of 5 mm×8 mm.

In one embodiment, the optical elements 502 a-c can be placedside-by-side. In some embodiments, the optical elements 502 a-c can bemounted on a common carrier (not shown). In other embodiments, theoptical elements 502 a-502 c can be mounted on separate carrier elements504 a-c to form the optical devices 500 a-c.

In one implementation, the optical devices 500 a-c can be arranged(e.g., mounted on a frame or structure) so as to be laterally offset bya predetermined amount. In such arrangement, the optical elements 502a-c are laterally offset from one another by a predetermined distance,along a direction that is parallel to a major surface of at least onecarrier element 504 a-c. Here, the emission surfaces can also beparallel to one another. In another implementation, the emissionsurfaces may not be parallel to one another, but may instead be angledrelative to one another.

As shown, the light from each optical element 502 a-c can be redirectedby the corresponding mirroring apparatus 506 a-c, so as to superimposethe image data, which can be collected via the optical combinerapparatus 508 (e.g., combiner optics such as a lens) to produce variouscolors. The light from each optical element 502 a-c can be varied basedon the control via the carrier elements 504 a-c, so as to producedifferent colors based on how much of each color from each opticalelement 502 a-c is emitted and then combined.

FIG. 6 is a diagram showing an illustration of physical separationbetween pixels within an optical device. It includes a plurality ofpixels 602 a-c, a plurality of light guides 604, a plurality of physicalseparations 606, a carrier element 608, an optical element 610, a bondinterface 612 between the carrier element 608 and optical element 610, aplurality of emitters 614 (light emitting regions), and a plurality ofcontact pads 616 of the carrier element 608 and the optical element 610.Light can be emitted from the light emitting surface of the emitters614, and can propagate through the pixel regions as shown.

In various embodiments, each pixel 602 a-c (e.g., monochromatic imageregion) can comprise one or a plurality of optical physical isolation orpixel isolation structures configured to limit crosstalk betweenneighboring regions of the optical element 610. For example, theisolation structures can comprise trenches formed through at least aportion of the optical element 610. The isolation structures may besimilar to the deep trench isolation structures implemented in back sideilluminated image sensors.

As shown, in one embodiment, the physical separation 606 between pixels602 a-c within an optical element 610, such as a chip, can comprise deeptrench isolation features for integrated microLED arrays. Such deeptrench isolation features can prevent light received by one pixel fromgoing into another, microLEDs can also be fabricated such that light 604generated by one diode/pixel is not scattered internally to theneighboring pixel/diode, based for example on the physical separation606. Based on such individually controllable pixel 602 a-c, lightemitted via the emitter 614 (which can be configured to emit light of asingle prescribed color, and make up or define at least a part of thepixel 602 a-c) from for example one pixel 602 c is physically isolatedfrom the adjacent pixel 602 b by the physical separation 606.

FIGS. 7A and 7B are diagrams showing different embodiments withdifferent physical separations. FIG. 7A is a diagram showing anillustration of physical separation 702 between every pixel 704, andFIG. 7B is a diagram showing an illustration of physical separation 706only in A×A matrix (for example, 2×2, 3×3, etc.) 708 of pixels 710. Theembodiment of FIG. 7B can produce a high yield because one (1)malfunctioning pixel may not be a concern for, e.g., the light emitted,since the physical separation is between the A×A matrices 708 ratherthan individual pixels 710. Such embodiment can also enable improvedcontrol of, e.g., brightness of the light emitted. The processorelement(s) (e.g., a CMOS or Si back plane) can control a selected numberof pixels from the matrix 708 to turn ON or OFF to control brightness,such that the matrix 708 can serve as one large pixel of a displaycomprising several smaller pixels 710. Thus, in various embodiments, theprocessor element(s) can independently control the pixels 710 as part ofthe matrix 708 to create desired image data, in which the matrix 708 canserve as a larger pixel and the pixels 710 can serve as sub-pixels. Thepixels 710 in an optical element can accordingly be divided intomatrices of pixels, and the processor element(s) can accordingly beconfigured to selectively control the brightness of pixels within eachmatrix. In various embodiments, the isolation features can be configuredto optically separate (e.g., prevent crosstalk) between adjacentmatrices 708 of pixels 710. In some embodiments, adjacent pixels 710within a matrix 708 may not be separated by isolation features. In otherembodiments, adjacent pixels 710 may be separated by isolation features.

FIG. 8 is a diagram showing an optical system 800 configured to directlight to a waveguide. It includes input coupling 802, a waveguide 804,and output coupling 806.

In one embodiment, the optical assemblies 400 and/or 500 such as withthe optical assemblies of combined LED-CMOS structure (includingmonochromatic microLED display) described herein can be attached asseparate units or mounted directly (for example via a plurality of inputcouplings 802) on the waveguide 804 in direct, side or angularconfiguration. In one or more implementations, this can be implementedin for example projectors (projection systems), car HUDs, smart watchdisplays, and cell phone displays, which include a plurality of outputcouplings 806, used to transmit the image data to the user's eye 102.

FIGS. 9 and 10 are diagrams showing optical devices such as microLEDsdirectly bonded to a waveguide 906, 1006 with input and outputcouplings. The devices each include optical assembly 902, 1002(described in detail herein with respect to for examples FIGS. 2-3 )configured to couple light to the waveguide 906, 1006, with inputcoupling (904 and 1004, respectively) and to the user with outputcoupling (908 and 1008, respectively). In some embodiments (e.g., FIG. 9), the bonded optical devices (e.g., the assembly 902) can be directlybonded to the waveguide 906 without an intervening adhesive tomechanically and optically couple the optical devices to the waveguide906. In other embodiments, the optical assembly can be mounted to aframe or other structure that connects to the waveguides.

The input coupling 904, 1004 allows the image data from the opticalassembly 902, 1002 to enter the waveguide 906, 1006 (for example made ofdielectric material), which is used to transfer the image data via light(including superimposed light emitted from the optical assembly 902,1002 via for example a corresponding array of emitters) travellingthrough the waveguide 906, 1006 by for example total internal reflection(TIR) and to the user's eye 102 via the output coupling 908, 1008.

In one embodiment, as shown in FIG. 10 , an optical apparatus 1010 (suchas for example a prism) can be used to redirect the light transmittedfrom the optical assembly 1002, so as to enable the light to travelthrough the waveguide 1006. In some embodiments, the optical assembly1002 can be mounted to another structure that is angled relative to thewaveguide 1006, and light can be redirected to the optical apparatus1010 by way of mirrors and combiner optics as shown.

FIG. 11 is a diagram showing an illustration of superposition of threecolor pixels. It includes a plurality of optical elements (e.g., LED die(R, G, B)) 1102 a-c including a plurality of pixels 1106, a carrierelement 1104, a plurality of optical combining elements 1108 (e.g.,lenses), a plurality of connecting waveguides 1110, a plurality ofmirroring apparatus 1112 a-c, an optical combiner apparatus 1114, and awaveguide 1116.

In one embodiment, the plurality of optical elements 1102 a-c can emit,via a plurality of emitters (not shown) monochromatic light, which cantravel through the corresponding optical combining element 1108 andconnecting waveguide 1110, to be reflected by the correspondingmirroring apparatus 1112 a-c. As shown, the plurality of opticalelements 1102 a-c can be disposed between the carrier element 1104 andthe waveguide 1116. The optical elements 1102 a-c can be directly bondedto the carrier element 1104 without an intervening adhesive.Furthermore, the mirroring apparatus 1112 a-c can be arranged at anangle relative to connecting waveguides 1110, so as to direct theincoming lights through the optical combiner apparatus 1114 and thewaveguide 1116 to the user's eye (not shown).

In one embodiment, the carrier element 1104 is a silicon/glass carrier,or an active silicon die driving the pixels 1106 and the opticalelements (such as for example LED die) 1102 a-c in another embodiment.In some embodiments, the optical elements can be directly bonded to thewaveguide, e.g., to the connecting waveguide 1110, without anintervening adhesive. In other embodiments, the optical elements can beattached to the waveguide with a transparent adhesive.

Thus, in various embodiments, a bonded optical device is disclosed. Thebonded optical device can include a first optical element having a firstarray of optical emitters configured to emit light of a first color. Thefirst optical element can be bonded to at least one processor element,the at least one processor element comprising active circuitryconfigured to control operation of the first optical element. The bondedoptical device can include a second optical element having a secondarray of optical emitters configured to emit light of a second colordifferent from the first color. The second optical element can be bondedto the at least one processor element. The at least one processorelement can comprise active circuitry configured to control operation ofthe second optical element. The bonded optical device can include anoptical pathway optically coupled with the first and second opticalelements, the optical pathway configured to transmit a superposition oflight from the first and second optical emitters to an optical output tobe viewed by a user.

In some embodiments, the first optical element is directly bonded to theat least one processor element without an intervening adhesive, and thesecond optical element is directly bonded to the at least one processorelement without an intervening adhesive. Respective dielectric bondingsurfaces of the first optical element and the at least one processorelement can be directly bonded to one another without an interveningadhesive. Respective conductive contact pads of the first opticalelement and the at least one processor element can be directly bonded toone another without an intervening adhesive. Each optical emitter of thefirst and second arrays of optical emitters can be electricallyconnected to a corresponding driver circuit on the at least oneprocessor element.

In some embodiments, a first optical emitter of the first array ofoptical emitters and a second optical emitter of the second array ofoptical emitters at least partially define a pixel, and the opticalpathway can be configured to transmit a superposition of the light fromthe first and second optical emitters of the pixel. The at least oneprocessor element can comprise a first processor element and a secondprocessor element separate from the first processor element. The firstoptical element can be bonded to the first processor element and thesecond optical element can be bonded to the second processor element. Insome embodiments, the at least one processor element comprises a commoncarrier.

In various embodiments, the optical pathway comprises an opticalwaveguide. The first optical element can be disposed between the opticalwaveguide and the first processor element. The second optical elementcan be disposed between the optical waveguide and the second processorelement. In some embodiments, the first and second optical elements aredirectly bonded to the optical waveguide without an interveningadhesive. In some embodiments, the first and second optical elements arebonded with one or more adhesives transparent to the respective firstand second colors of light.

In some embodiments, the first and second optical elements can belaterally offset from one another along a direction parallel to a majorsurface of the at least one processor element. In some embodiments,respective emission surfaces of the first and second optical elementscan be generally parallel to one another. In some embodiments,respective emission surfaces of the first and second optical elementscan be disposed non-parallel to one another.

The bonded optical device can include one or a plurality of opticalisolation structures in the first optical element. The optical isolationstructures can be configured to limit crosstalk between adjacent opticalemitters.

In some embodiments, the first color has a first peak at a firstwavelength, the second color has a second peak at a second wavelength. Adifference between the first and second wavelengths can be at least 25nm. Thus, in various embodiments, the wavelengths can be separated by asufficient amount such that the colors emitted by the optical elementscan be distinguishable from one another. In some embodiments, theoptical pathway can include one or more redirection elements (e.g.,mirrors, beamsplitters, etc.) to redirect light from the first andsecond image regions. In some embodiments, the optical pathway comprisesa lens configured to act upon the superimposed light.

The bonded optical device can include a third optical element opticallycoupled with the optical pathway and bonded to the at least oneprocessor element. The third optical element can be configured to emitlight of a third color that is different from the first and secondcolors. The first, second, and third colors can comprise red, green, andblue, respectively. In various embodiments, the optical emitters of thefirst array are independently controllable. The first and second arraysof optical emitters can comprise respective arrays of light emittingdiodes (LEDs). A pitch of the optical emitters of the first array can beless than 50 microns. A pitch of the optical emitters of the first arraycan be less than 10 microns.

In another embodiment, a bonded optical device is disclosed. The bondedoptical device can include a first optical element directly bonded to atleast one carrier without an adhesive, the first optical elementconfigured to emit light of a first color. The bonded optical device caninclude a second optical element directly bonded to the at least onecarrier without an adhesive. The second optical element can beconfigured to emit light of a second color different from the firstcolor. The first and second optical elements can be laterally offsetfrom one another along a direction parallel to a major surface of the atleast one carrier. The bonded optical device can include an opticalpathway optically coupled with the first and second optical elements,the optical pathway configured to transmit a superposition of light fromthe first and second optical elements to an optical output to be viewedby a user.

In some embodiments, the at least one carrier comprises a first carrierand a second carrier separate from the first carrier. In someembodiments, the at least one carrier comprises at least one processorelement comprising active circuitry configured to control operation ofat least one of the first and second optical elements. In someembodiments, the first optical element can be directly bonded to the atleast one carrier without an intervening adhesive, and the secondoptical element can be directly bonded to the at least one carrierwithout an intervening adhesive. In some embodiments, respectivedielectric bonding surfaces of the first optical element and the atleast one carrier are directly bonded to one another without anintervening adhesive. In some embodiments, respective conductive contactpads of the first optical element and the at least one carrier aredirectly bonded to one another without an intervening adhesive. Invarious embodiments, the at least one carrier comprises at least one ofsilicon or glass. In some embodiments, the at least one carrier can havea coefficient of thermal expansion (CTE) less than 7 ppm.

In some embodiments, the optical pathway can comprise an opticalwaveguide. In some embodiments, a third optical element can be opticallycoupled with the optical pathway. The third optical element can bedirectly bonded to the at least one carrier without an adhesive. Thethird optical element can be configured to emit light of a third colorthat is different from the first and second colors.

In some embodiments, the first, second, and third colors comprise red,green, and blue, respectively. The first and second optical elements cancomprise respective arrays of optical emitters. The optical emitters canbe independently controllable. The optical emitters can comprise lightemitting diodes (LEDs).

In another embodiment, a method of bonding at least one optical elementwith at least one processor element is disclosed. The method can includebonding a first optical element with to at least one processor element,wherein the first optical element comprises a first array of opticalemitters configured to emit light of a first color, and the at least oneprocessor element comprises active circuitry configured to controloperation of the first optical element; bonding a second optical elementwith to the at least one processor element, wherein the second opticalelement comprises a second array of optical emitters configured to emitlight of a second color different from the first color, and the at leastone processor element comprises active circuitry further configured tocontrol operation of the second optical element; and coupling the firstand second optical elements with an optical pathway, the optical pathwayconfigured to transmit a superposition of light from the first andsecond optical emitters to an optical output to be viewed by a user. Insome embodiments, the at least one carrier comprises a processor die.

Although disclosed in the context of certain embodiments and examples,it will be understood by those skilled in the art that the presentinvention extends beyond the specifically disclosed embodiments to otheralternative embodiments and/or uses and obvious modifications andequivalents thereof. Further, unless otherwise noted, the components ofan illustration may be the same as or generally similar to like-numberedcomponents of one or more different illustrations. In addition, whileseveral variations have been shown and described in detail, othermodifications, which are within the scope of this disclosure, will bereadily apparent to those of skill in the art based upon thisdisclosure. It is also contemplated that various combinations orsub-combinations of the specific features and aspects of the embodimentsmay be made and still fall within the scope of the present disclosure.It should be understood that various features and aspects of thedisclosed embodiments can be combined with, or substituted for, oneanother in order to form varying modes of the disclosed invention. Thus,it is intended that the scope of the present invention herein disclosedshould not be limited by the particular disclosed embodiments describedabove, but should be determined only by a fair reading of the aspectsthat follow.

What is claimed is:
 1. A bonded optical device comprising: a firstoptical element having a first dielectric bonding surface, a firstplurality of conductive pads, and a first array of optical emittersconfigured to emit light of a first color, the first dielectric bondingsurface directly bonded to at least a second dielectric bonding surfaceof at least one processor element without an intervening adhesive, theat least one processor element further comprising a second plurality ofconductive contact pads and active circuitry configured to controloperation of the first optical element, wherein the first plurality ofconductive contact pads of the first optical element and the secondplurality of conductive contact pads of the at least one processorelement are directly bonded and electrically connected to one anotherwithout an intervening adhesive; a second optical element having asecond array of optical emitters configured to emit light of a secondcolor different from the first color, the second optical elementdirectly bonded to the at least one processor element without anintervening adhesive, the at least one processor element comprisingactive circuitry configured to control operation of the second opticalelement; and an optical pathway optically coupled with the first andsecond optical elements, the optical pathway configured to transmit asuperposition of light from the first and second optical emitters to anoptical output to be viewed by a user.
 2. The bonded optical device ofclaim 1, wherein each optical emitter of the first and second arrays ofoptical emitters is electrically connected to a corresponding drivercircuit on the at least one processor element.
 3. The bonded opticaldevice of claim 1, wherein a first optical emitter of the first array ofoptical emitters and a second optical emitter of the second array ofoptical emitters at least partially define a pixel, and wherein theoptical pathway is configured to transmit a superposition of the lightfrom the first and second optical emitters of the pixel.
 4. The bondedoptical device of claim 1, wherein the at least one processor elementcomprises a common carrier.
 5. The bonded optical device of claim 1,wherein the first and second optical elements are laterally offset fromone another along a direction parallel to a major surface of the atleast one processor element, wherein respective emission surfaces of thefirst and second optical elements are generally parallel to one another.6. The bonded optical device of claim 1, wherein respective emissionsurfaces of the first and second optical elements are disposednon-parallel to one another.
 7. The bonded optical device of claim 1,wherein the optical pathway comprises one or more redirection elementsto redirect light from the first and second image regions, and whereinthe optical pathway comprises a lens configured to act upon thesuperimposed light.
 8. The bonded optical device of claim 1, furthercomprising a third optical element optically coupled with the opticalpathway and bonded to the at least one processor element, the thirdoptical element configured to emit light of a third color that isdifferent from the first and second colors.
 9. The bonded optical deviceof claim 1, wherein the optical emitters of the first array areindependently controllable.
 10. The bonded optical device of claim 1,wherein the first and second arrays of optical emitters compriserespective arrays of light emitting diodes (LEDs).
 11. The bondedoptical device of claim 1, wherein a pitch of the optical emitters ofthe first array is less than 50 microns.
 12. The bonded optical deviceof claim 1, wherein a pitch of the optical emitters of the first arrayis less than 10 microns.
 13. The bonded optical device of claim 1,wherein each of the first and second arrays of optical emitters comprisea plurality of matrices, each matrix including a plurality of pixels,the at least one processor element configured to selectively control thebrightness of pixels within each matrix.
 14. The bonded optical deviceof claim 13, further comprising isolation features between adjacentmatrices of pixels.
 15. The bonded optical device of claim 1, whereineach of the first and second optical elements is configured to create arespective monochromatic image.
 16. The bonded optical device of claim1, wherein the at least one processor element comprises a firstprocessor element and a second processor element separate from the firstprocessor element, the first optical element bonded to the firstprocessor element and the second optical element bonded to the secondprocessor element.
 17. The bonded optical device of claim 16, whereinthe optical pathway comprises an optical waveguide, wherein the firstoptical element is disposed between the optical waveguide and the firstprocessor element, and wherein the second optical element is disposedbetween the optical waveguide and the second processor element.
 18. Thebonded optical device of claim 17, wherein the first and second opticalelements are directly bonded to the optical waveguide without anintervening adhesive.
 19. A bonded optical device comprising: a firstoptical element having a first array of optical emitters configured toemit light of a first color, the first optical element directly bondedto at least one processor element without an intervening adhesive, theat least one processor element comprising active circuitry configured tocontrol operation of the first optical element; a second optical elementhaving a second array of optical emitters configured to emit light of asecond color different from the first color, the second optical elementdirectly bonded to the at least one processor element without anintervening adhesive, the at least one processor element comprisingactive circuitry configured to control operation of the second opticalelement, and wherein the at least one processor element comprises afirst processor element and a second processor element separate from thefirst processor element, the first optical element bonded to the firstprocessor element and the second optical element bonded to the secondprocessor element; and an optical pathway optically coupled with thefirst and second optical elements, the optical pathway configured totransmit a superposition of light from the first and second arrays ofoptical emitters to an optical output to be viewed by a user.
 20. Thebonded optical device of claim 19, wherein the optical pathway comprisesan optical waveguide, wherein the first optical element is disposedbetween the optical waveguide and the first processor element, andwherein the second optical element is disposed between the opticalwaveguide and the second processor element.
 21. The bonded opticaldevice of claim 20, wherein the first and second optical elements aredirectly bonded to the optical waveguide without an interveningadhesive.
 22. The bonded optical device of claim 19, wherein a firstdielectric bonding surface of the first optical element and a seconddielectric bonding surface of the at least one processor element aredirectly bonded to one another without an intervening adhesive.
 23. Thebonded optical device of claim 22, wherein a first plurality ofconductive contact pads of the first optical element and a secondplurality of conductive contact pads of the at least one processorelement are directly bonded and electrically connected to one anotherwithout an intervening adhesive.
 24. A bonded optical device comprising:a first optical element having a first dielectric bonding surfacedirectly bonded to at least a second dielectric bonding surface of acarrier without an intervening adhesive, the first optical elementconfigured to emit light of a first color; a second optical elementdirectly bonded to the carrier without an intervening adhesive, thesecond optical element configured to emit light of a second colordifferent from the first color, the first and second optical elementslaterally offset from one another along a direction parallel to a majorsurface of the carrier; and an optical pathway optically coupled withthe first and second optical elements, the optical pathway configured totransmit a superposition of light from the first and second opticalelements to an optical output to be viewed by a user.
 25. The bondedoptical device of claim 24, wherein the at least one carrier comprises afirst carrier and a second carrier separate from the first carrier. 26.The bonded optical device of claim 24, wherein the at least one carriercomprises at least one processor element comprising active circuitryconfigured to control operation of at least one of the first and secondoptical elements.
 27. The bonded optical device of claim 24, wherein afirst plurality of conductive contact pads of the first optical elementand a second plurality of conductive contact pads of the at least onecarrier are directly bonded to one another without an interveningadhesive.
 28. The bonded optical device of claim 24, wherein the atleast one carrier comprises at least one of silicon or glass.
 29. Thebonded optical device of claim 24, wherein the optical pathway comprisesan optical waveguide.
 30. The bonded optical device of claim 24, furthercomprising a third optical element optically coupled with the opticalpathway, the third optical element directly bonded to the at least onecarrier without an adhesive, the third optical element configured toemit light of a third color that is different from the first and secondcolors.
 31. The bonded optical device of claim 24, wherein the first andsecond optical elements comprise respective arrays of optical emitters.32. A method of bonding at least one optical element with at least oneprocessor element, the method comprising: directly bonding a firstdielectric bonding surface of a first optical element to at least asecond dielectric bonding surface of at least one processor elementwithout an intervening adhesive, and directly bonding and electricallyconnecting a first plurality of conductive contact pads of the firstoptical element to a second plurality of conductive contact pads of theat least one processor element without an intervening adhesive, whereinthe first optical element comprises a first array of optical emittersconfigured to emit light of a first color, and the at least oneprocessor element comprises active circuitry configured to controloperation of the first optical element; directly bonding a secondoptical element to the at least one processor element without anintervening adhesive, wherein the second optical element comprises asecond array of optical emitters configured to emit light of a secondcolor different from the first color, and the at least one processorelement comprises active circuitry further configured to controloperation of the second optical element; and coupling the first andsecond optical elements with an optical pathway, the optical pathwayconfigured to transmit a superposition of light from the first andsecond arrays of optical emitters to an optical output to be viewed by auser.